How to run a query to find a string in blob files?

Question

Mediawiki has a table in the database 'text' which contains the page content. It is saved as a [BLOB] file. I would like to run a query to search through all the text on the site to see which pages contain a certain 'string'. How do I run a query to search [blob] files?

Solution

The Mediawiki markup text is stored in the old_text field, which is a mediumblob type. You can query it like any other text-based field. MySQL will cast your string into binary for the query. Note that this is a case-sensitive search!

select old_id from text where old_text like "%string%";

If you need case-insensitivity then you need to apply an appropriate character set with a case-insensitive collation to the column:

SELECT old_id from text where CONVERT(old_text USING latin1) like '%STRing%';

Be aware that if your table isn't small these queries will take a long time.